n. pl. de·on·tol·o·gies
1. Ethical or moral theory concerned with duties and rights.
2. The doctrine that ethical status of an action lies in its adherence to a set of rules.
[Greek deon, deont-, obligation, necessity (from neuter present participle of dein, to need, lack; see deu-1 in the Appendix of Indo-European roots) + -LOGY.]
de·on′to·logi·cal (-tə-lŏjĭ-kəl) adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.